The ultimate goal of this project is to determine whether beta-adrenergic blocking drugs lower blood pressure by an action in the central nervous system that includes alteration of noradrenergic nerve activity. We have determined that propranolol causes a selective increase in norepinephrine turnover in the corpus striatum, cerebal cortex and cerebellum with no changes occurring in the medulla, midbrain-hippocampus or hypothalamus. Other beta-blockers such as timolol and butoxamine cause a decrease in whole brain norepinephrine turnover. In future studies we plan to determine the effect of a large number of beta-blocking drugs on norepinephrine release in six discrete brain regions and attempt to correlate these changes with the antihypertensive effect of these drugs.